﻿Public Class Form1
  Private Sub MaskedTextBox1_MaskInputRejected(
      ByVal sender As System.Object, ByVal e As  _
      System.Windows.Forms.MaskInputRejectedEventArgs) _
      Handles MaskedTextBox1.MaskInputRejected
    MessageBox.Show("Dati inseriti non validi")
  End Sub
End Class
